Radiant tubular heat exchanger



Jan. 2, 1962 G. STEINERT 3,015,319

RADIANT TUBULAR HEAT EXCHANGER Filed Jan. 22, 1958 2 Sheets-Sheet 1INVEN'IIQIQNERT GERHARD S {27 2s s4 s5 HG. 2 BY 55 29 503132 23 A AGENTJan. 2, 1962 G. STEINERT RADIANT TUBULAR HEAT EXCHANGER 2 Sheets-Sheet 2Filed Jan. 22, 1958 M m w 1/ uucmuodno/w cn H00 :0 one 00 00 0a 000:"0000000;

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United States Patent 3,015,319 RADIANT TUBULAR HEAT EXCHANGER GerhardSteinert, Stuttgart, Germany, assignor to Kohlenscheidnngs-Gesellschaftm.b.H., a corporation of Germany Filed Jan. 22, 1958, Ser. No. 710,508 2Claims. (Cl. 122-478) The invention relates to a radiant tubular heatexchanger more specifically to a radiant tubular steam heater asprovided in a steam generator having furnace walls that are lined withwater-cooled tubes, and comprising parallelly disposed tubular wallpanels spaced from each other a substantial distance to prevent thebridging over of slag.

In a steam boiler having a furnace equipped with fluid cooled walls,undesirable peaks of temperature are encountered in the combustion gasesproduced in the lower portion of the furnace, as these gases rise andpass through the upper portion of the furnace. These peaks oftemperature are the result of the cooling effect of the tube linedfurnace walls in the vicinity thereof, and cause unequal heat absorptionin the panel heat exchanger disposed in the upper part of the furnacechamber. Such unequality in temperature not only necessitates theemployment of a greater amount of heating surface because of the lessefficient use made thereof, but also requires a more liberal use ofcostly tube material that is capable of withstanding higher gastemperatures, all of which is highly undesirable both from thestandpoint of first cost as well as maintenance costs.

Various means have been employed heretofore to eliminate or reducetemperature peaks in the rising gas stream. One design proposes anincrease in the distance between the tubular panels as these panelsapproach the side walls of the furnace. However, since a minimumdistance of approximately two feet is required between the panels toprevent the bridging over of the slag deposited thereon during operationof the furnace, it follows that the larger spacing employed near thefurnace walls will reduce the total amount of heating surface that canbe installed in a given furnace width thereby increasing the temperatureof the gases entering the succeeding convection heating surfaces andcausing undesirable slag deposits thereon.

In attempting to solve the present problem it was also proposed in thepast to lengthen those tube panels which are located at or near thecentral portion of the furnace chamber. However, to be fully efiectivesuch lengthening must be extensive and calls for an increase in furnaceheight in order to avoid the overheating and burning of the thuslyextended tube portions, unless costly higher temperature alloy materiflis made use of in the tubes to a greater extent.

The present invention has as its primary object a solution of the aboveproblem without the need of taking into the bargain the above-reciteddisadvantages. This is expediently accomplished by providing a heatexchanger in the upper portion of the furnace chamber which comprises arow of widely spaced tubular panels parallelly disposed with respect toeach other and to the side walls, and in which each panel adjacent theside walls is being formed by a row of tubes having a sum total oftubular circumferences which is smaller than the combined circumferencesof the tubes comprising each of the remaining panels, i.e., those whichare located in the central zone of the furnace chamber.

Another related object of the invention is to provide a steam heater inthe upper portion of the furnace constructed of widely spaced tubularpanels, each panel adjacent the side walls comprising a row of tubesthat are spaced a greater distance apart than the tubes that form thepanels more remotely located from the side walls.

Patented Jan. 2., 1962 Still another object of the steam heater in theupper portion of the furnace chamber of a radiant steam generator inwhich the outer tube panels, those located near the side walls have asmaller total horizontal width than the tube panels located near thecenter of the furnace chamber.

Other objects and advantages of the invention will become apparent fromthe following description of illustrative embodiments thereof when takenin conjunction with the accompanying drawings wherein:

FIG. 1 shows an elevational diagrammatic view of a steam power plantoperating under the reheat cycle and being equipped with the hereindisclosed inventive improvement;

FIG. 2 is a fractional front elevational section of the radiationchamber and steam heater of the steam boiler illustrated in FIG. 1 whentaken on line 2-2 thereof;

FIG. 3 is a plan view taken on line 3'3 of FIG. 2;

FIG. 4 is another elevational front section of a furnace and a. steamheater similar to that shown in FIG. 2 but disclosing my invention asapplied to a. single superheater;

FIG. 5 is a diagrammatic plan view taken on line 5-5 of FIG. 4;

FIG. 6 represents a front elevational section of a furnace and radiantsingle superheater wherein the direction of steam flow has been reversedfrom that shown in the embodiment of FIGS. 4 and 5;

FIG. 7 is a diagrammatic plan view taken on line 7--7 of FIG. 6;

FIGS. 8, 9, 10 and 11 show various cross sections taken through steamheaters embodying the basic feature of my invention, i.e., that ofproviding the tube panels near the side walls with a smaller,circumferential total dimension than the tube panels remote from theside walls.

Referring now to the drawings wherein like reference characters are usedthroughout to designate like elements, "FIG. 1 illustratively shows asteam generating power plant having a furnace 2 including a lowercombustion chamber 3 and a top-jacently adjoining radiation chamber 4.The walls of the furnace 2 include front wall 6, rear wall 8 and sidewalls 10 and 12. Fuel and air are discharged into the combustion chamber3 for burning by way of burners 13 which preferably are arranged fortangential firing. The hot gases produced rise upwardly giving off heatto the furnace walls 6, 8, 10 and 12 which are lined with water carryingand steam generating tubes 14. These gases are further cooled by passingconsecutively over other heating surfaces disposed in the upper portion4 of the furnace, in an adjoining horizontal gas ofitake 15 and in avertical gas pass 16. The gases are finally discharged into theatmosphere by way of induced draft fan 17 and stack 18. Water wall tubes14, terminate in a steam and water drum 19 and deliver a mixture ofsteam and water into the drum wherein the steam is separated from thewater by means, not shown. The water flows downwardly through downcomers20 and enters the water wall tubes 14 by way of headers 21 and 22thereby completing the circulation circuit. The steam separated from thewater is conducted from drum 19 to a convection superheater 24 locatedin the horizontal gas pass 15 and then to a radiant superheater 26 whichis disposed in the upper portion of the furnace or radiation chamber 4.In the embodiment shown in FIG. 2, radiant superheater 26 comprises aseries of spacedly disposed panels 29, 30, 31, 32, 33 located in thecentral portion of chamber 4 and arranged in parallel relation with eachother and with the side walls 10, 12 of the furnace.

Each of the panels 29 to 33 comprises a plurality of closely spacedU-tubes nested to form a panel wall as indicated in FIG. 1. Eachvertical leg of these tubes is connected to an inlet header 38 or anoutlet header 40 invention is to provide a.

respectively. Inlet header 38 receives steam from con- 42 by'way'ofanoutlet header 40 and steam pipe 44.

Having expended some of its energy in the turbine, the steam is conducedto a convection reheater 46 disposed in thevertical gas pass 16, fromwhence the steam flows via pipe 41 to inlet header 43 of radiantreheater 48 located in the radiation chamber 4.' Reheater '48 is formedof two sections 48a and 481) (FIG. 2) having parallelly disposed spacedtubular walls similar to those used in constructing radiant superheatersection 26. In the preferred embodiment'shown in FIG. 2 reheater section4812 comprises tubular panels 27 and 28 and reheater section 485 panels34 and 35. After'being heated to the desired temperature the steampasses through outlet headers 45 and steam pipe 42 to the low pressurestageof steam turbine 42. i

In accordance with the present invention the reheater panels aredisposed adjacentthe side walls and 12 each panel being formed oftubes-having a smaller total circumference when measured in a horizontalplane than the tubes which form superheater tube panels 29, 30, 31, 32and 33 located remotely from the side walls.

FIGS. 4, '5, 6 and 7 illustratively show twoembodiments of my'inventionas applied to a single superheater 50 occupying the entire width of theradiation chamber 4. Superheater 50-is divided into two sections 51 and52, one half of section 51 being located adjacent each side wall 10,12and section 52 being located in the central zone of radiation chamber'4.In accordance with the inventionsuperheater portion 51 comprises tubularwall panels 53, 55 each being formed of a plurality of closelyspacedtubes the combined circumferences of these tubes being smallerthan the combined circumferences of' the tubes-that form the ubularpanels of the centrally located portion 52. r w i More specifically, inFIGS. 4 and 5, there ,is shown a superheater in which the steam to beheated enters the outer sections 51 by way of headers 54. After havingpassed through the tubes of sections 51 the steam enters headers 56 andis conducted via pipes 58 to the header 60 of the centrally locatedsection 52. While passing through the tubes of section 52 the steam isheated to the final temperature and is conducted to a source of'usebyway of header 62 and suitable piping, not shown.

The single superheater illustrated of a design similar to that shown inFIGS. 4 and 5, however, distinguishes therefrom by a reversal of thedirection of flow of the steam as indicated by arrows. Thus the steamenters header 62, flows through the U-shaped tubes of section 52 andleaves by wayof header 66 to be conducted via steam pipe 58 and headers56 into superheater portions 51 where the steam is heated to its finaltemperature and conducted to a point of use; by way of headers 54 andsuitable steam piping, not shown.

I As earlier set forth wherein the superheater portions 51 adjacent theside walls 16 and 12 are formed of tubes having a smaller combinedcircumference for each tubular panel Wall than the tubes forming thepanels of the centrally located portion 52.

Similarly, as earlier stated, the reheater tubular panels 27, 28,34 and35 of FIG. 2 each comprise a plurality of'tubes having a smaller sumtotal of circumferences than the tubes forming the centrally locatedsuperheater panels 29, 30, 31, 32 and 33.

FIGS. 8, 9, l0 and 11 illustrate some preferred design features of thetube panels of a radiant steam heater,

which is in accordance with my invention, and which fulfill the designconditions set'forth in the two preced- 1 ing paragraphs, designconditions which must be met to accomplish the, objects of my invention.

Thusin the embodiment of FIG. 8, this is accomplished by a steamheaterarrangement having uniform in FIGS. 6 and 7 is 4 tube spacingwherein the outermost panels 64 are of a horizontal width which issubstantially less than the width of the centrally located panel 70. Thepanels 66 and 68 located intermediate panels 64 and 70 have a widthwhich gradually increases with the distance of these panels from thenearest side wall, Panels 64, 66 and 68 can be arranged symmetricallyabout axis A-A as illustratively shown in FIG. 8, or these panels can bearranged adjacent the gas otftake 15 as indicated in FIG. 9.

Or, the width of the vided into two or more between front wall 6 andFIG. 10.

Furthermore, in accordance with my invention and as illustratively shownin FIG. 11, the spacing of the tubes forming panels 64, 66 and 68increases as the location of these panels approaches the nearest sidewall 10 or 12, thereby presenting to the gases a sum total ofcircumferences in each panel which is not only smaller than the combinedcircumferences of the tubes forming panels 64, 66 and 68 can bediportions which are distributed gas oiftake 15 as illustrated in acentrally located panels 70 but which gradually decreases as the nearestside wall is approached.

The various arrangements shown in FIGS. 8, 9, l0 and 11 can equally wellbe applied to;a reheat steam generator such asthat illustrated in FIGS.1, 2 and 3, or to a steam generator equipped with a single superheatersuch as thatshownin FIGS. 4, 5, 6 and 7.

In FIGS. 4, and 5 is shown a steam heater in which the relatively coolsteam "first flows through the outer sections:51 and is heated to thefinal temperature by passing through the central section 52. Such anarrangement advantageopsly leads to a more uniform flow velocity of thesteam through all of the tubes because the progressive increase of thesteam volume due to heating is accompanied by a progressive increase inflow area.

On the other hand, FIGS. 6 and 7 illustrate a steam heater organizationwherein'the flow ofsteam is reversed, i.e., the relatively cool steamfirst flows through the centrally located, highly heated section 52 andis brought to the final temperature by passingthrough the outer sections51. Such a flow arrangement advantageously permits the'finalheatingstage to takeplace in a moderate temperature zone which resultsin economical advantage with respect to the use of hightemperature alloymaterial. In-addition the higher flow velocities attained in the outersection tend to promote a more elfective cooling of the tube walls.

In conclusion, the problem precipitated by the cooling efi'ect of theside Walls 10 and 12 upon the gases causing non-uniform temperaturedistribution across the furnace width and the width .of the gas ofltake15 is successfully metby my inventively improved-design of a panel typeradiant steamheater as herein disclosed. My invention imposes a heatabsorption pattern upon the gas steam which largely erases theseinequalities in gas temperature and eliminates to a substantial degreethe disadvantages resulting therefrom.

such changes, as fall within the purview of my invention.

What I claim is:

1. In a radiant heat exchanger having a combustion chamber for thegeneration of hot gases by the burning of fuel and a ton-jacentlyadjoining radiation chamber having two parallel side walls lined withheat absorbing. tubes, said heat absorbing wall'tubes creatingparallellyflowing vertical zones of gas of non-uniform temperaturecharacteristic when .measured 'in a horizontal plane, with thetemperature of. the-centrally located. gas zonebeinghigherthan thetemperature of the side wall adjacent gas zones, the combination of arow of upright tubular wall panels spacedly disposed across the upperportion of said radiation chamber in parallel relation to the heatabsorbing tubes lining said side walls and to each other, each panelcomprising a plurality of parallelly spaced tubes carrying a gaseousmedium to be heated by absorbing radiant heat from the hot gasesgenerated in said combustion chamber, the lineal circumference whenmeasured in a horizontal plane, per rated gas flow area, of the tubesforming the said tubular panels that are adjacent said side walls beingsubstantially smaller than the corresponding lineal circumference of thetubes forming the tubular panels located adjacent the centre of saidvradiation chamber, and said upright tubular panels being divided intoserially connected groups including a first group located adjacent saidside walls and a second group occupying a central location Within saidradiation chamber, said first group having means for receiving saidgaseous medium to be heated, means for progressively increasing thetemperature thereof while advancing said medium thro'ughthe tubes ofsaid first group, said second group having means for receiving saidmedium from said first group, means for progressively increasing thetemperature thereof while advancing said medium through the tubes ofsaid second group, and means for discharging said gaseous medium fromsaid second group after having been heated.

2. in a radiant steam generator having a combustion chamber for thegeneration of hot gases by the burning of fuel and a top-jacentlyadjoining radiation chamber having two parallel side walls lined withheat absorbing tubes, said heat absorbing Wall tubes creating parallellyflowing vertical zones of gas of non-uniform temperature characteristicwhen measured in a horizontal plane, with the temperature of thecentrally located gas zone being higher than the temperature of the sideWall adjacent gas zones,

the combination of a row of upright tubular wall panels spacedlydisposed across the upper portion of said radiation chamber in parallelrelation to the heat absorbing tubes lining said side Walls and to eachother, each panel comprising a plurality of parallelly spaced tubescarrying steam to be heated by absorbing radiant heat from the hot gasesgenerated in said combustion chamber, the lineal circumference whenmeasured in a horizontal plane, per rated gas flow area, of the tubesforming said tubular panels that are adjacent said side walls beingsubstantially smaller than the lineal circumference of the tubes formingthe tubular panels located adjacent the centre of said radiationchamber, and said upright tubular panels being divided into seriallyconnected groups with respect to steam flow including a first panelgroup solely occupying the space adjacent said side walls and a secondpanel group solely occupying a space remote from said side walls withinsaid radiation chambensaid second group having inlet means for receivingprimary steam, exclusive of reheat steam, from said steam generator forsuperheating and outlet means for discharging said steam aftersuperheating to a turbine, and said first group having means forreceiving steam, exclusive of primary steam, from the high pressurestage of said turbine for reheating.

References Cited in the file of this patent UNITED STATES PATENTS1,996,099 Cooper Apr. 2, 1935 2,075,067 Snyder Mar. 30, 1937 2,685,279Caracristi Aug. 3, 1954 2,821,175 Seidl Ian. 28, 1958 FOREIGN PATENTS624,769 Germany I an. 29, 1936 899,503 Germany Dec. 14, 1953

